Milo g



(No Model.)

M. G. KELLOGG. MULTIPLE SWITGHBOARD.

No 592,393. Patented Oct. 26,1897.

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MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLO GG SIVITCIIBOARD AND SUPPLY COMPANY, OF SAME PLACE.

M ULTIPLE SWITCH BOARD.

SPECIFICATION forming part of Letters Patent NO. 592,393, dated October 26, 1897.

Application filed May 14:, 1891. Serial No. 392,720. (No model.)

To all whom it may concern.-

Be it known that I, MILO G. KELLOGG, of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Switchboards for Telephone-Exchanges, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to a telephone-exchange system in which the lines are metallie-circuit lines.

Briefiystated, the invention consists in connecting two or more metallic-circuit telephone-lines to a single switching device or jack, and in the case of multiple switchboards to a switch on each board. In the arrangement of multiple boards shown two pairs of telephone-lines are connected with the different switches on the boards, there being on each board one switch for each pair of lines. Each switch has two pairs of contact-pieces suitably placed and insulated, the two sides of one line of a pair of lines being respectively connected with two contactpieces of its switch, and the two sides of the other line of the pair being respectively connected with the other pair of contacts of said switch.

The invention further consists in switchplugs, apparatus, and connections by which, with such lines and switch connections, the calls of the subscribers may be received and promptly attended to and the usual operations of the exchange gone through with.

My invention is illustrated by the accompanying drawings, in which-- Figure 1 is a diagram illustrative of four metallic-circuit lines, normally grounded on one side at the central ofiice, connected on two different switchboards, with the switches for said lines and annnnciators and retardation-coils for said normally-grounded lines. Fig. 2 is a diagram of an operators plug and cord system and apparatus to be used at the switchboards. Fig. 3 is a View of one of the switch-plugs, and Fig. 4 is a diagram of an op erators test system to be used at each board.

The switches of the lines on the two boards are marked a. a and b h, the two former being located 011 the two boards shown and the two as will hereinafter be described.

latter being also located on shown, respectively.

Z Z are the switch-holes through the fronts of rubber strips 011 which the metal parts of the switches are mounted. are square. On opposite sides of the holes are insulated pairs of contact-pieces g g. On the other sides of the holes are insulated pairs of contact-pieces jj. There is one pair of contacts g g and one pair of contacts for each switch.

Four lines are shown in the drawings. Line a is connected with the pairs of contacts g g of switches a a, and line a with pairs of contact-piecesjj of the same switches. In like manner lines I) and b are connected with the pairs of contacts g g and jj, respectively, of switches b b.

N N are annunciator-s, and X X are retardation-coils, one annunciator and one retarda tion-coil for each line. The line is connect-ed the two boards to the ground through its annunciator and retardation-coil and the annunciator is located at the board where the calls of the line are to be answered.

In Fig. 2, D D are a pair of switch-plugs adapted to be inserted into any switch at their board and to form connections when inserted, a n are the rubber insulations of the plugs, while m m and m m are two pairs of contact-pieces of a plug. WVhen a plug is inserted into a switch, it may be inserted in such a direction that its pieces at m form connection with pieces 9 g and its pieces m m form connection with pieces jj of the switch, or in such reverse direction that m m form connection Withj j and m on form connection with g g, respectively. For each plug there is a switching device, into which any other plug located at its board may be placed and which has two contact-pieces which connect with the contact-pieces m m of the plug thus inserted. The contact-pieces of this switching device are connected through flexible switch-conductors with contact-pieces m in of their plug. These switching devices are marked 8 s. The contact-pieces m m and m m of a There is one test- These holes battery B for each pair of plugs with cords. In Fig. 2 but one pair of plugs, with their cords, are shown. Other pairs may be added as required for each operator in the manner substantially as shown and as will be apparent to those skilled in the art.

In the operators test system shown in Fig.

' the two sides of the line and, bringing her telephoneintocircuit with the cords, finds out what line is wanted. She then tests the line wanted, as will hereinafter be described, and it she finds the line to be free or not in use she connects the other plug of the pair with its switch, as will be described, and may then send a calling-current to the lines. and finally leave them in condition for conversation. In connecting with the line wanted the operator places the switch-phi g in the switch connected with theline in suchadirection that the two contact-pieces m m of the plug form connection with the two contact-piecesot the switch which are connected with the twosides of the.line, provided there is not already another plug in the-switchx If, however, there is another plug, in the switch, she places theplug with which she to make the desired connection into. the switching device of the plug which is in the switch in such a direction that the contact-pieces m m of the plug form connection with the contact-pieces of the switching device.

The. test system is asfollows: Whenever-a line is. switched in acolnplete metallic circuit for conversation, there is a test-battery in circuit with it, and when it is not thus switched it. has: no battery in its circuit. The testplugis connected with a line, as will hereinafter be described, when the line is tested. It follows. that inasmuch as the complete metallic-circu-it'of two lines switched together are grounded through their annunciators and, retardation-coilsand has a test-battery in circuit, and that the test plug is grounded through the test receiving instrument the instrument will sound or respond when either line thus tested is switched for conversation, while, when the test is madeof an unswitched' line, having no battery in circuit, the instrument will notv respond. The operator can therefore determine on testing any linewhether or notit is. switched for use.

making the connection toa line for testing the; operator will. place the contact-pieceof the testplug on. one of the switch contactpieces connected with the line, "providing there is no switch-plug in the switch. If, however, there is aswitch-plug in the switch, she will place her test-plugin connection with one of the contact-pieces of the switching device of the plug.

With this system and organization for mul tiple switchboards for metallic-circuit lines only one-half as many switches are required for a given number of lines, and practically twice as many lines can be placed in a given space as in the usual multiple-switchboard system. It therefore practically doubles the board.

I claim as my invention-- 1. In a telephone-exchange system, metallic circuit lines divided into pairs and switches for said lines on a switchboard, one switch for each pair of lines, each switch having two pairs of contact-pieces to which the two lines of its pair are respectively connected, the two sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces ot' the other pair, in combination with pairs of switch plugs, the plugs having each a pair of contact-pieces and the two contactpieces of one plug being connected by flexible conducting-circuits with the two contactpieces of the other plug of the pair, each plug being adapted to be inserted into each switch intwo positions or directions, in one of which its said contact-pieces are connected with the contact-pieces of one pair of contact-pieces of the switch and in the other of which they are connected with the other contact-pieces of the switch, respectively substantially as set forth.

2'. In a telephone-exchange system, metallic-circuit lines the two sides of which are normally open at the central office, divided into pairs and switches for said lines on a switchboard, one switch for each pair of lines each switch having two pairs of contact-pieccs to. which the two lines of its pair are respectively connected, the two sides of one line to i the two-contact-pieces of one pairand the two sides of theother line to the two contact-pieces 3 oi the other-pair, in combination with pairs of switch-plugs, the plugs having each a pair of contact-pieces and the two contact-pieces of one plug being connected by flexible conducting-circuits, with the two contact-pieces i of the other plug, of the pair, each plug being adapted to-be-inserted into each switch in two gpositions or directions, in one of which its gsaid contact-piecesare connected with the contact-pieces of onepai r of the con tact-pieces of the switch and in the other of which they iare connected with the other contact-pieces ';of the switch, respectively, substantially as 5 set forth.

' 3. ln a. telephoneexchange system, telegphone-lines divided intopairs and switches Efor said lines, on aswitchboard, one switch for each pair of lines, each switchhaving two capacity of a given sized multiple switchpairs of contact-pieces to which the two lines of its pair are respectively connected, the two sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair, in combination with pairs of switch-plugs, the plugs having each a pair of contact-pieces and the two contact-pieces of one plug being connected by flexible conducting circuits with the two contact-pieces of the other plug of the pair, each plug having also a second pair of contact-pieces and a switching device for each plug with two contact-pieces connected by flexible conductors with said second pair of contact-pieces of the plug each plug being adapted to be inserted into each switch in two positions or directions, in one of which its said first-mentioned contact-pieces are connected with the contact-pieces of one pair of the contact-pieces of the switch and its said second-mentioned contact-pieces are connected with the other contactpieces of the switch and in the other of which the firstmentioned contact-pieces of the plug are connected with the second-mentioned contactpieces of the switch and the second-mention ed contact-pieces of the plug are connected with the flrstmentioned contact pieces of the switch, each plug being also adapted to be inserted into each of said switching devices and when inserted to connect its said first-mentioned contact-pieces with said contact-pieces of the switching devices respectively, sub stantially as set forth. 7

4. In a telephone-exchange system, metallic-circuit lines the two sides of which are normally open at the central office, divided into pairs and switches for said lines, on a switchboard, one switch for each pair of lines, each switch having two pairs of contact-pieces to which the two lines of its pair are respectively connected, the two sides of one line to the two contact-pieces, of one pair and the two sides of the other line to the two contactpieces of the other pair, in combination with pairs of switch-plugs, the plugs having each a pair of contact-pieces and said contactpieces of a plug being connected by flexible conductin g-circuit with the two contact-pieces of its'mate each plug having also a second pair of contact-pieces anda switching device with a pair of contact-pieces connected by flexible conductors with said second pair of contact-pieces of the plug each plug being adapted to be inserted into each switch in two positions or directions, in one of which its said first-mentioned contact'pieces are connected with the two contact-pieces of one pair of contact-pieces of the switch and its secondmentioned contact-pieces are connected with the other contact-pieces of the switch and in the other of which the firstmentioned contact-pieces of the plug are connected with the second-mentioned contactpiece of the switch and the second-mentioned contact-pieces of the plug are connected with the first'mentioned contact-pieces of the switch, each plug being also adapted to be inserted into each of said switching devices and when inserted to connect its said firstmentioned contact-pieces with said contactpieces of the switching device respectively, substantially as set forth. I

5. In a telephone-exchange system, multiple switchboards, metallic-circuit lines divided into pairs and switches for said lines, one switch for each pair of lines on each of said boards, each switch having two pairs of contact'pieces to which the two lines of its pair are respectively connected, the two sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair, in combination with pairs of switch-plugs at each board, the plugs having each a pair of c011- tact-pieces and the two contact-pieces of a plug being connected by flexible conductingcircuits with the contact-pieces of its mate, each plug being adapted to be inserted in two positions or directions into each switch at its board, in one of which its said contactpieces are connected with the two contactpieces of one pair of the contact-pieces of the switch and in the other of which they are connected with the other contact-pieces of the switch, respectively, substantially as set forth.

6. In a telephone-exchange system, multiple switchboards, metallic-circuit lines the two sides of which are normally open at the central office divided into pairs and switches for said lines, one switch for each pair of lines on each of said boards, each switch having two pairs of contact-pieces to which the two lines of its pair are respectively connected, the two sides of one line to the two cont-actpieces of one pair and the two sides of the other line to the two contact-pieces of the other pair,in combination with pairs of switchplugs at each board, the plugs having'each a pair of contact-pieces and the two contactpieces of one plug being connected by flexible conducting-circuits with the two contactpieces of its mate each plug being adapted to be inserted in two positions or directions into each switch at its board, in one of which its said contact-pieces are connected with the two contact-pieces of one pair of the contactpieces of the switch and in the other of which they are connected with the other contactpieces of the switch, respectively, substantially as set forth.

7. In a telephone-exchange system, multiple switchboards, metallic-circuit lines divided into pairs and switches for said lines, one switch for each pair of lines on each of said boards, each switch having two pairs of contact-pieces to which the two lines of its pair are respectively connected, the two sides of one line to' the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair, in combination with pairs of switch-plugs at each ed to be inserted into each of said switching tact-pieces and said contact-pieces of a plug being connected by flexible conducting-circuits with the two contact-pieces of its mate, each plug having also a second pair of contact-pieces anda switching device for each plug located at its board with two contactpieces connected by flexible conductors with said second pair of contact-pieces of the plug, each plug being adapted to be inserted into each switch in two positions or directions, in one of which its said first-mentioned contactpieces are connected with the two contactpieces of one pair of contact-pieces of the switch and its said second-mentioned contactp-ieces are connected with the other contactpieces of the switch and in the other of which thefirst-mentioned contact-pieces of the pin g are connected with the second-mentioned contact-pieces of the switch and the second-mentioned contact-pieces of the switch are connected with the first mentioned contactpieces of the plug, each plug being also adaptdevices at its board and when inserted toconneet its said first-mentioned contact-pieceswith said contactpieces of the switching device, respectively, substantially as set forth.

8. In a telephone-exchange system, metallic-circuit telephone-lines divided into pairs and switches for said lines on a switchboard, one switch for each pair of lines, each switch having two pair's of contact-pieces to which the two' lines of its pair are respectively connected, the two sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair, in combination with pairs of switch-plugs, the plugs having each a pair of contactrpieces and the contact-pieces of a ping being connected by flexibleconductingcircuits with the contact-pieces of its mate each plug being adaptedto be inserted into each switch in two positions or directions in one of which its said contact-pieces are connected with the contact-pieces of one pair of the contact-pieces of the switch and inthe other of which they are connected with the other contact-pieces of theswi-tch, anda testbattery in one of said circuits between each pair of plugs, substantially as set forth.

- 9. In a telephone-exchange system, metallic-circuit telephone-lines grounded at the central office and divided into pairs and switches for said lines on a switchboard, one switch for each pair of lines, each switch having, two pairs of contact-pieces to which the two lines of itspair are respectively connected-,the two sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair, in combination with pairs of switch-plugs, the plugs having each a pair of contact-pieces and the contact-pieces of a plug. being connected by flexible conductingcircuitswith the two contact-pieces of its mate, each pl'u-g'being adapted to be inserted intoea'ch switch in two positions or directions,

- in one of which its said contact-pieces are connected with the contact-pieces of one pair 3 of the contact-pieces of the switch and in the other of which they are connected with the 5 other contact-pieces of the switch, and a test- 5 battery in one of said conducting-circuits be- 1 tween each pair of plugs, substantially as set forth.

10. In a telephone-exchange system, multiple switchboards, metallic telephone-lines divided into pairs and switches for said lines, one switch for each pair of lines on each of said boards, each switch havingpairs of two contact-pieces to which the two lines of its pair are respectively connected, the two sides of one line to the two'contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair, in combiuation with pairs of switch-plu gs at each board, I the plugs having each a pair of contact-pieces and the two contact-pieces of a plug being con-- nected by flexible conducting-circuits with the two contact-pieces of its mate each ping being adapted to be inserted in two positions or directions into each switch at its board, in one of which its said contact-pieces are connected with the two contact-pieces of one pair of the contact-pieces of the switch and in the other of which they are connected with the other contact-pieces of the switch, and a testbattery in one of said conducting-circuits between each pair of plugs, substantially as set forth.

11. In a telephone-cxchange system,- multi-. ple switchboards, metallic-circuit telephonelines, grounded at the central office and divided into pairs and switches for said linesone switch for each pair of lines on each of said ;boards, each switch having two pairs of contact-pieces to which the two lines of itspair are respectively connected the two sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair, in combination with pairs of switch-plugs at each board, the plugs having each a pair of contact-piecesand isa'i'd two contact-pieces of a plug being con- ;nected by flexible conducting-circuits with the two contact-pieces of its mate, each plug ,1 being adapted to be inserted in twopositi'ons I or directions into each switch at its board, in 5 one of which its said contact-pieces are coni nected with the two contact-pieces of one pair I of the contact-pieces of the switch and in the other of which they are connected with the 5 other contact-pieces of the switch, and a testbattery in one of said conducting-circuits b'etween each pair of plugs, substantially asset forth.

12. In a telephone-exchange system,-1nu'ltiple switchboards, metallic-circuit telephone- 1 pair are respectively connected, the two'sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair, in combination with pairs of switch-plugs at each board, the plugs having each a pair of contact-pieces and said contact-pieces of a plug being connected by flexible conducting-circuits with the two contact-pieces of its mate, a test-battery in one of each of such conducting-circuits, each plug having also a second pair of contact-pieces and a switching device for-each plug at its board with two contactpieces connected through flexible conductors with'said second pair of contact-pieces of the plug, each plug being adapted to be inserted into each switch at its board in two positions or directions, in one of which its said firstmentioned contactpieees are connected with the contact-pieces of one pair of contact-pieces of the switch and its said second-mentioned contact-pieces are connected with the other contact-pieces of the switch and in the other of which its said first mentioned contactpieces are connected with said second-mew tioned contact-pieces of the switch and its said second mentioned contactpieces are connected with said first-mentioned contactpieces of the switch, each plug being also adapted to be inserted into each of said switching devices at its board and when inserted to connect its said first-mentioned contactpieces with said contact-pieces of the switching device, respectively, substantially as set forth.

13. In atelephone-exchange system, metallic-circuit telephone-lines grounded on one of their sides and divided into pairs and switches for said lines on a switchboard, each switch having two pairs of contact-pieces to which the two lines of its pair are respectively connected the two sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair, in combination with pairs of switch-plugs, the plugs having each a pair of contact-pieces and said contact-pieces of a pin g being connected by flexible conductingcircuits with the two contact pieces of its mate, a test-battery in one of such flexible conducting-circuits, each plug being adapted to be inserted into each switch in two positions or directions, in one of which its said contact-pieces are connected with the contact-pieces of one pair of the contact-pieces of the switch, and in the other of which they are connected with the other contact-pieces of the switch, and a test receiving instrument grounded on one side and connected on its other side to a test plug or device adapted to be brought into connection with any of said contact-pieces of said switches, substantially as set forth.

14. In a telephone-exchange system, multiple switchboards, metallic-circuit telephonelines grounded on one of their sides and divided into pairs and switches for said lines one switch for each pair of lines on each of said boards, each switch having two pairs of contact-pieces to which the two lines of its pair are respectively connected, the two sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair, in combination with pairs of switch-plugs at each board, the plugs having each a pair of contact-pieces and the two contact-pieces of a plug being connected by flexible conductingcircuits with the two contact-pieces of its mate, a testbattery in one of such conducting-circuits, each plug being adapted to be inserted into each switch at its board in two positions or directions, in one of which its said contact-picces are connected with the contact-pieces of one pair of said contactpieces of the switch andin the other of which they are connected with the other contactpieces of the switch, and test receiving instruments, one at each board, each instrument being grounded on one side and connected on its other side to a test plug or de vice adapted to be brought into connection with any of said contact-pieces of said switches at its board, substantially as set forth.

15. In a telephone-exchange system, multiple switchboards, metallic-circuit telephonelines the two sides of which are normally open at the central office grounded on one of their sides and divided into pairs, and switches for said lines, one switch for each pair of lines on each of said boards, each switch having two pairs of contact-pieces to which the two lines of its pair are respectively connected, the two sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair, in combination with pairs of switch-plugs at each board, the plugs having each a pair of contact-pieces and the two contact-pieces of a plug being connected by flexible conducting-circuits with the two contact-pieces of its mate, a test-battery in one of such conducting-circuits, each plug being adapted to be inserted into each switch at its board in two positions or directions, in one of which its said contact-pieces are connected with the contact-pieces of one pair of the contact-pieces of the switch and in the other of which they are connected with the other contact-pieces of the switch, and test receiving instruments, one at each board, each instrument being grounded on one side and connected on its other side to a test plug or de' vice adapted to be brought into connection with any of said contact-pieces of said switches at its board, substantially as set fort-h.

16. In a telephone-exchange system, multiple switchboards, metallic-circuit telephone+ lines grounded on one of their sides and divided into pairs and switches for said lines, one switch for each pair of lines on each of said boards, each switch having two pairs of contact-pieces to which the two lines are respectively connected, the two sides of one line-to the two contact-pieces of one pair and the two sides of the otherline to the two contact-pieces of the other pair, in combination with pairs of switch-plugs at each board, the plugs having each .a pair of contact-pieces and the two contact-pieces of a plug being connected by flexible conducting-circuits with the two contactpieces of its mate, a test-battery in one of such conducting-circuits, each plug having also a second pair of contact-pieces and a switching device for each plug at its board with two contact-pieces connected through flexible conductors with said last-mentioned contactpieces of the plug, each plug being adapted to be inserted into each switch at its board in two positions or directions, in one of which its said first-mentioned contact-pieces are connected with the contact-pieces of one pair of the contact-pieces of the switch and its secondmentioned contact-pieces are connected with the other contact-pieces of the switch and in the other of which its said first-mentioned contact-pieces are connected with the second mentioned contact-pieces of the switch and its said second-mentioned contact-pieces are connected with the first-mentioned contact-pieces of the switch, each plug being also adapted to be inserted into each of said switching devices at its board and when inserted to connect its said first-mentioned contact-pieces with said contact-pieces of the switching device, and test receiving instruments, one at each board, each grounded on one side and connected on its other side to a test plug or device adapted to be brought into connection with any of said contact-pieces of said switches and switching devices at its board, substantially as set forth.

17. In atelephone-exchange system, metallic-circuit telephone-lines divided into pairs and switches for said lines on a switchboard, one switch for each pair of lines, each switch having two pairs of contact-pieces to which the two lines of its pair are respectively connected, the two' sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair, in combination with aswitch plughavin g a pair of contact-pieces connected through flexible conductors to the two sides of one of said lines, and adapted to be inserted into either of said switches in two positions or directions in one of which its said contactpieces are connected with the contact-pieces of one pair of the contact-pieces of the switch and in the other of which its said contactpieces are connected with the other contactpieces of the switch, substantially as set forth.

18. In a telephone-exchange system, metallic-circuit lines grounded at the central office and divided into pairs and switches for said lines on a switchboard, one switch foreach pair of lines, each'switch having two pairs of contact-pieces to which the two lines of its pair are respectively connected, the two sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair, in combination with retardation-coils, one for each line and in its ground connection, pairs of switclrplugs, the plugs having each a pair of contact-pieces and the contact-pieces of a plug being connected by flexible conductingcircuits with the two contact pieces of its mate, each plug being adapted to be inserted into each switch in two positions or directions, in one of which its said contact-pieces are connected with the contact-pieces of one pair of the contact-pieces of the switch and in the other of which they are connected with the other contact-pieces of the switch, and a testbattery in one of said conducting-circuits between each pair of plugs, substantially as set forth.

19. In a telephone-exchange system, multiple switchboards, metallic-circuit telephonelines, grounded at the central oiflce and divided into pairs and switches for said lines one switch for each pair of lines 011 each of said boards, each switch having two pairs of contactpieces to which the two lines of its pair are respectively connected the two sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair, in combination with retardation-coils, one for each line and in its ground connection pairs of switch-plugs at each board, the plugs having each a pair of contact-pieces and said two contact-pieces of a plug being connected by flexible conducting-circuits with the two con tact pieces of its mate, each plug being adapted to be inserted in two positions or directions into each switch at its board, in one of which its said contact-pieces are connected with the two contact-pieces of one pair of the contact-pieces of the switch and in the other of which they are connected with the other contact-pieces of the switch, and a test-battery in one of said conductingcircuits between each pair of plugs, substantially as set forth.

20. In atelephone-exchange system, nietallic-circuit telephone-lines grounded on one of their sides and divided into pairs and switches for said lines on a switchboard, each switch having two pairs of contact-pieces to which the two lines of its pair are respectively connected the two sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair,'in combination with retardation-coils, one for each line and in its ground connection pairs of switch-plugs, the plugs having each a pair of contact-pieces and said contact-pieces of a plug being connected by strunient grounded 011 one side and connected on its other side to a test plug or device adapted to be brought into connection with any of said contact-pieces of said switches, substantially as set forth.

21. In a telephone-exchange system, multiple switchboards, metallic-circuit telephonelines grounded on one of their sides and divided into pairs and switches for said lines, one switch for each pair of lines on each of said boards, each switch having two pairs of contact-pieces to which the two lines are respectively connected, the two sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contactpieces of the other pair, in combination with i'etardatioucoils, one for each line and in its ground connection pairs of switch-plugs at each board, the plugs having each a pair of contact-pieces and the two contact-pieces of a plugbeing connected by flexible conductingcircuits with the two contact-pieces of its 1nate,a test-battery in one of such conductingcircuits, each plug having also a second pair of conta-ct pieces and a switching device at its board with two contact pieces connected through flexible conductors with said lastinentioned contact-pieces of the plug, each plug being adapted to be inserted into each switch at its board in two positions or directions, in one of which its SZLIClfilSll-IILGDUODGCI contact'pieces are connected with the contactpieces of one pair of contact-pieces of the switch and its second-mentioned contactpieces are connected with the other contactpieees of the switch and in the other of which its said first-mentioned contact-pieces are connected with the second-mentioned contact-pieces of the switch and its said secondinentioned contact-pieces are connected with the first-mentioned contact pieces of the switch, each plug being also adapted to be illserted into each of said switching devices at its boards and when inserted to connect its said first-n1entioned contact-pieces with said contact-pieces of the switching device, and test receivinginstruments, one at each board, each grounded on one side and connected on its other side to a test plug or device adapted to be brought into connect-ion with any of said contact pieces of said switches and switching devices at its board, substantially as set forth.

22. In a telephoneexchange system, metallic-circuit lines grounded at the central office and divided into pairs and switches for said lines on a switchboard, one switch for each pair of lines, each switch having two pairs of contact-pieces to which the two lines of its pair are respectively connected, the two sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair, in combination with annunciators, one for each line and in its ground connection, pairs of switchplugs, the plugs having each a pair of contact-pieces and the contact-pieces of a plug being connected by flexible conducting-circuits with the two contact-pieces of its mate, each plug being adapted to be inserted into each switch in two positions or directions, in one of which its said contact-pieces are connected with the contact-pieces of one pair of the contact-pieces of the switch and in the other of which they are connected with the other contact-pieces of the switch, and a testbattery in one of said eonducting-circuits between each pair of plugs, substantially as set forth.

23. In a telephone-exchange system, multiple switchboards, metallic-circuit telephonelines, grounded at the central ofiice and di vided into pairs and switches for said lines one switch for each pair of lines on each of said boards, each switch having two pairs of contactpieces to which the two lines of its pair are respectively connected the two sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair, in combination with annunciators one for each line and on its ground connection pairs of switchplugs at each board, the plugs having each a pair of contact-pieces and said two contactpieces of a plug being connected by flexible conducting -circuits with the two contactpieces of its mate, each plug being adapted to be inserted in two positions or directions into each switch at its board, in one of which its said contact-pieces are connected with the two contact-pieces of one pair of the contactpieces of the switch and in the other of which they are connected with the other contactpieces of the switch, and atest-battery in one of said conducting-circuitsbetween each pair of plugs, substantially as set forth.

24. Ina telephone-exchange system, metallic-circuit telephone-lines grounded on one of their sides and divided into pairs and switches for said lines on a switchboard, each switch having two pairs of contactpieces to which the two lines of its pair are respectively connected the two sides of one line to the two contact-pieces of one pair and the two sides .of the other line to the two contact-pieces of the otherpair, in combination with annunciators, one for each line and in its ground connection pairs of switch-plugs, the plugs having each a pair of contact-pieces and said contact-pieces of a plug being connected by flexible conductingcircuits, with the two contact-pieces of its mate, a test-battery in one of such flexible conducting-circuits, each plug being adapted to be inserted into each switch in two positions or directions in one of which its said contact-pieces are connected with the contact-pieces of one pair of the contact-pieces of the switch, and in the other of which they are connected with the other contact-pieces of the switch, and a test receiving instrument grounded on one side and connected on its other side to a test plug or device adapted to be brought into connection with any of said contact-pieces of said switches, substantially as set forth.

25. In a telephone-exchange system, multi-. ple switchboards, metallic-circuit telephonelines grounded on one of their sides and divided into pairs and switches for said lines, one switch for each pair of lines on each of said boards, each switch having two pairs of contact-pieces to which the two lines are respectively connected, the two sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair, in combination with annunciators one for each line and in its ground connection pairs of switch-plugs at each board, the plugs having each a pair of contact-pieces and the two contact-pieces of a plug being connected by flexible conducting-circuits with the two contact-pieces of its mate, a test-battery in one of such conducting-circuits, each plug having also a second pair of contact-pieces and a switching device at its board with two contact-pieces connected through flexible conductors with said lastmentioned contact-pieces of the plug, each plug being adapted to be inserted into each switch at its board in two positions or directions, in one of which its said first-mentioned contact-pieces are connected with the contact-pieces of one pair of contact-pieces of the switch and its second-mentioned contactpieces are connected with the other contactpieces of the switch and in the other of which its said first-mentioned contact-pieces are connected with the second-mentioned contact-pieces of the switch and its said. secondmentioned contact-pieces are connected with the firstmentioned contact pieces of the switch, each plug being also adapted to be inserted into each of said switching devices at its boards and when inserted to connect its said first-mentioned contact-pieces with said contact-pieces of the switching device, and test receiving instruments, one at each board, each grounded on one side and connected on its other side to a test plug or device adapted to be brought into connection with any of said contact pieces of said switches and switching devices at its board, substantially as set forth.

26. In a telephone-exchange system, metallic-circuitlines divided into pairs and switches for said lines on a switchboard, one switch for each pair of lines, each switch having two pairs of contact-pieces to which the two lines of its pair are respectively connected, the two sides of one line to the two contact-pieces of one pair and the two sides of the other line to the two contact-pieces of the other pair, in combination with switching devices by which any two of said lines may be connected in metallic circuit for conversation.

I11 testimony whereof I have hereunto subscribed my name.

MILO G. KELLOGG.

Witnesses:

FRANK S. OBER, EDWARD C. DAVIDSON. 

